The present invention relates generally to aluminum alloys and more specifically to heat treatable aluminum alloys strengthened by L12 phase dispersions that are useful at temperatures from about −420° F. (−251° C.) up to about 650° F. (343° C.).
The combination of high strength, ductility, and fracture toughness, as well as low density, make aluminum alloys natural candidates for aerospace and space applications. However, their use is typically limited to temperatures below about 300° F. (149° C.) since most aluminum alloys start to lose strength in that temperature range as a result of coarsening of strengthening precipitates.
The development of aluminum alloys with improved elevated temperature mechanical properties is a continuing process. Some attempts have included aluminum-iron and aluminum-chromium based alloys such as Al—Fe—Ce, Al—Fe—V—Si, Al—Fe—Ce—W, and Al—Cr—Zr—Mn that contain incoherent dispersoids. These alloys, however, also lose strength at elevated temperatures due to particle coarsening. In addition, these alloys exhibit ductility and fracture toughness values lower than other commercially available aluminum alloys.
Other attempts have included the development of mechanically alloyed Al—Mg and Al—Ti alloys containing ceramic dispersoids. These alloys exhibit improved high temperature strength due to the particle dispersion, but the ductility and fracture toughness are not improved.
U.S. Pat. No. 6,248,453 discloses aluminum alloys strengthened by dispersed Al3X L12 intermetallic phases where X is selected from the group consisting of Sc, Er, Lu, Yb, Tm, and U. The Al3X particles are coherent with the aluminum alloy matrix and are resistant to coarsening at elevated temperatures. The improved mechanical properties of the disclosed dispersion strengthened L12 aluminum alloys are stable up to 572° F. (300° C.). U.S. Patent Application Publication No. 2006/0093512 by the current inventor discloses an aluminum magnesium alloy strengthened with a dispersion of Al3X dispersoids with the L12 structure where X comprises Sc, Gd, and Zr. The alloy provides excellent mechanical properties in the temperature range of about −420° F. (−250° C.) up to about 573° F. (300° C.).
An aluminum magnesium alloy strengthened by L12 precipitates with excellent mechanical properties in the temperature range of about 420° F. (−250° C.) to about 650° F. (343° C.) would be useful.